#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;

int Fib(int n) {
	if (n == 1) return 1;
	else if (n == 2) return 1;
	else {
		return Fib(n - 1) + Fib(n - 2);
	}
}
int main()
{
	int n;
	cin >> n;
	cout << Fib(n);
	return 0;
}